The present invention relates to the trucking industry, and more particularly to a pneumatic or hydraulic controlled stabilizer assembly for the steering mechanism in vehicles.
Recently, the Federal Government issued new weight restrictions and regulations for trucks using federal highways. These laws make it economically feasable to add a third axle to a vehicle, which in turn permits more payload to be carried. These third or "lift" axles, however, have inherent problems which cause premature tire wear and frame stress. To avoid such problems, manufacturers of these suspensions have developed a steerable lift axle that casters, and which is not connected to a steering mechanism. Many states have in fact recently passed laws requiring lift axles to be steerable. A problem plaguing the users of such lift wheels is one of instability and a lack of centering. It has been found that standard-type steering stabilizers do not solve this problem.
Steering stabilizers are used in trucks and other vehicles to reduce sway and to stabilize front end suspensions. These devices also dampen shocks resulting from external objects meeting the wheels during travel. In the past, such stabilizers have been automotive shock absorber devices designed strictly for steerable axles that are connected to a steering mechanism. To date, the only assemblies provided steerable, liftable axles have been automotive shock absorbers used in conjunction with coil springs. A problem exists in that such combination assemblies have proved unreliable in controlling the axles, when applied to liftable axles.
A related problem involves the need to maintain the lift wheels of a truck or other vehicle in a straight position when the wheels are raised. This need has been met in the past by using steering dampers in conjunction with a two-coiled spring centering system. Too often, however, one side of the system would overpower the other due to spring breakage or fatigue and destroy the bias or centering capability. This would result in marked shaking, vibration or wobble of the vehicle; and once this shimmying movement begins, the springs accentuate the side-to-side motion, due to their inherent design.
There exists a need, therefore, for a steering stabilizer which can be used on steerable, liftable axles in which the movable steering linkage is not connected to a steering mechanism.
There also exists a need for such a stabilizer in which it is impossible for one side of the system to overpower the other and thereby destroy the bias for the positive center position.
There exists a further need for a steering stabilizer that eliminates the use of springs, which tend to suffer fatigue and breakage, along with accentuating the side-to-side motion.